…building civilizations with my space elves in space.

thermal superconductor

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So, I gather more’n a few laser fans are coming to visit these days, so just to save time, here’s the canonical reason that lasers are the ‘verse’s secondary weapons system, not its primary one:

(It turns out that this is really a recapitulation of points raised in Non-Standard Starship Scuffles, so if you’re already nodding along to that, you can more or less skip the rest. I’ll just hit a few high points.)

Lasers, for the most part, are useful weapons systems under many circumstances. (Obviously they have to be, given their use as point-defense; if you couldn’t get effective results from lasing a k-rod, they wouldn’t be used.) As mentioned elsewhere, you can get an effective result out of a laser weapon, due to collimation, up to around a light-second, which is the entirety of the inner engagement envelope, and as such every military starship mounts a passel of phased-array plasma lasers for point-defense, and larger classes cram in some broadside offensive lasers too.

You can actually collimate reasonably effective beams at rather longer distances than that, as the existence of starwisp tenders demonstrates – although they themselves are of little use for military purposes despite the incidents mentioned in that article, seeing as they shift angular vector and alter their focus with all the grace and speed of apatosauruses mating. One would, however, make a dandy generator for a laser web.

(Yes, they exist in the ‘verse, and have done ever since the Admiralty paid the Spaceflight Initiative to launch Sky-Shield, the homeworld’s first orbital defense grid, back in the day. Orbital defense grids remain their main military use, along with civilian beamed power.)

It’s just that the IN sees no particular point in paying in either cashy money or mass/volume budget for collimation to make them effective beyond the inner engagement envelope, because you aren’t going to hit any actively evading targets at that range anyway, golden BBs and spies having gotten you a copy of their drunkwalk algorithms aside, and kinetics/AKVs work better for the geometry games played in the outer envelope.

Here, though, is the spoiler in the deck where military lasers are concerned:

Thermal Superconductors.

(The laws of physics do permit them, I am assured, and local materials science is more than up to producing them.)

In up-to-date designs, starship armor is woven through with a dense mesh of the stuff, with wicking into big heat-sink tanks of thermal goo. This causes something of a problem for weaponized lasers, because it makes it ridiculously hard to create a hot spot that’ll vaporize – instead, you just add heat to the whole starship. Which is not useless by any means, if you can manage lots of repeated hits or keep a beam on target, because if you can pump enough heat into a starship, either it, the crew, or both, will go into thermal shutdown; but this is what lasers are for in ‘verse starship combat. If you want to blast things apart, you go for kinetics, because you can’t tank (sic) big lumps of baryons.

Of course, this defense has its limitations: a laser grid at short range can hit its target with enough power to overcome the armor and, indeed, to chop its target neatly into a pile of small cubes. But that’s for definitions of short range meaning “inside knife-fight range”, and any Flight Commander who let the range close that much without having his entire propulsion bus shot off first would be summarily cashiered for incompetence.

And that’s why lasers aren’t the primary or only weapons system around these parts.

This applies especially to lighthuggers, inasmuch as an antimatter torch at high burn can be detected for light years even if you’re not the star system that it’s pointed at. If you are, all the more so. Much the same goes, at least for the destination system, for even the best-collimated of the launch lasers starwisps use. Any way you look at it, there’s no way to be subtle when engaging in near-luminal travel.

But it applies to everyone else, too. Even small reaction-drive burns – and vector-control drives of similar energy consumption – are bright enough to be seen most of the way across the system, and more to the point, the heat of operating life-support systems for biosapiences – or even the waste heat for the minimum technology needed to support digisapiences – stands out like a searchlight against the 3K sky background.

It’s not impossible to manage a degree of sneakiness. It involves making use of thermal superconductors to capture your emissions in most or even all directions, and heat pumps (which, let us not forget, generate even more heat which you have to then capture) to capture them in heat sinks – which will fill up and roast you if you keep it up for very long, so be careful about how long you need to use them. It involves making maximum use of cover – cold objects in space to hide behind, and hot objects to hide in front of, while being careful not to visibly occult anything, and always pointing the right bits of your ship in the right direction (observer-dependent, so best hope the system’s not busy). It involves limiting your propulsion to careful use of (hideously slow and inefficient) cold-gas thrusters and leveraging vector-control to get a tow from other ships or celestial bodies (in which case, being careful to ensure that you keep your effect on their apparent mass below the threshold that will trigger alerts in their engineering department or your target’s paranoid skywatching AIs.). And, of course, essentially none of this will help if someone happens to look out the wrong window or point a telescope in the wrong direction and spot you visually.

But it’s difficult and constrained enough – especially since you have to enter systems via the choke-points of their stargates – or suffer the above lighthugger problems – that it’s usually much easier to pretend to be something other than what you are, or bury yourself inside an asteroid big enough to act as a decent thermal sink, or get an insider agent to plant a You Can’t See Me data worm in their traffic-control systems, or otherwise engage in some kind of tactics that are more masquerade and less outright stealth.

(The ontotechnological engineers are working on – well, technically, working on the possible theory that might just possibly begin to underlie the engineering principles of – an actual bona-fide cloaking device that bypasses at least some of these difficulties. Still some awkward implications from physics, though: firstly, it’s inescapably double-blind, so while no-one can see you, you can’t see out either. The possibilities for things to go horribly wrong for you while you can’t see them are… large. Secondly, it involves basically hiding behind the domain wall of your own personal baby universe, possibly the only thing that does retain heat with 100% efficiency, which is to say, it actually makes the heat dissipation problem worse. Better have really good heat sinks, or you’ll cook yourself to death in really short order… and then release all that heat in a nice position-illuminating flare anyway.)

As a side note of things mentioned elsewhere on the defensive side, the chief purpose of lasers as ship-to-ship weapons is for pumping heat into the enemy. The defense against this is twofold: one, thermal superconductor (or, previously to the invention of this particular piece of exotic material, mere thermal-very-good-conductor-convector-etc.) plating to avoid localized hot spots heating up and exploding, and lots of goo of very high thermal heat capacity to dump heat into and then pump overboard. This doesn’t stop you from eventually having to heave to, extend your radiators, and quit the fight, but it does slow down getting to that point rather a lot. Similar plating to the former used in personal armor makes personal laser-arms, while not unuseful on the battlefield, certainly not the most useful thing which you can carry.

tl;dr They have their place in combat, but they’re not magically supreme on the field, and indeed are unlikely to be your primary weapons.

Also, while it would certainly be technologically possible to attach them to cyborg sharks, so far as I know, it’s never actually been done.

Instant Cooldown: No, no, no. Thermodynamics does not work that way, and even with thermal superconductors, neutrino pumps, and black holes, thermodynamics still doesn’t work that way. Stay out of the red zone.

(Also, bearing in mind the proclivities of the manufacturers of much of this equipment, the red line on the dial is where it will explode, not 10% before where it will explode on the assumption that many of the operators will be gung-ho idiots. Yes, there’s a safety margin to cover manufacturing variances, and suchlike. There is not one to protect you from yourself, as lying to you for your own good is not in their paradigm, belike.)

Deflector Shields: These come in one played-straight kind: kinetic barriers, which are a product of vector control (a kind of Applied Phlebotinium, yes), essentially applying counterforce to, or slapping aside, incoming massy objects, from space dust to missiles, but don’t do anything to massless radiation. And they’re usually ad-hoc plates, not an always-on bubble, but details…

The universe is not nearly so kind when it comes to providing us with a way of shielding against EM radiation, massless photon phenomenon that it is (and no, you can’t shield against lasers by making the hull shiny; it still heats up, explodes, and then isn’t shiny any more). The best they can do for this one, apart from the layers of shielding compound, and bunkerage and suchlike stashed under the hull, is for the hull plating and underlying layers to include a nice framework of thermal superconductor nanocomposite (at which thermodynamics weeps, but it is actually allowed by physics as we know them); this dissipates radiative heating throughout the entire structure of the ship, thus preventing exploding hot-spots. Of course, it doesn’t avoid the problem that if you keep acquiring heat faster than you can dump it – and remember, you generally can’t use your radiators when in combat – you’ll broil yourself.

To deal with that, military ships generally carry a few big tanks of thermal goo, a thick, goopy substance engineered to have a ludicrously high specific heat capacity, into which tanks heat generated during combat, specifically including what happens when you get hit by a medium-range energy weapon, is dumped. And when the thermal goo heats up enough that it’s no longer useful, it’s simply pumped over the side, taking its heat with it.

Which doesn’t solve the problem, but does significantly extend the time before you have to choose between surrender and broiling yourselves alive.

There is absolutely no way to shield against gravitic weapons except by counterfiring your own gravitic weapons extremely quickly and accurately, but honestly, if you’ve somehow managed to end up within (extremely short, by space standards) gravy range, you’re already totally screwed.